Shock strut



Apnl 16, 1940. c. v. JQANS'QN y 2,197,474

SHOCK STRUT Filed May 19, 1957 4latina! pr. 1c, 1940 2,197,474

UNITED lSTATES PATENT OFFICE snoer; simm- Carl V. Johnson, South Bend, Ind.. assigner to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Application may 19, 1931, 'serial No. 143,456

` 1 claim. (ci. 267-64) This invention relates to shock absorbers, and embodiment which includes a cylindrical casing more particularly to shock absorbing struts for |02 having threaded in its lower end a diaphragm airplanes. or support |04 secured against displacement as` It has been found highly desirable in shock by a welding bead |06. The head also serves to' 5 absorbing struts for airplanes to provide suitable seal the lower end of the casing against leakage, 5

` means for absorbing the initial shock of landing and suitably mounted on the support |04 is a A without rebound, and means eiective after the metering pin |00 of the conventional type.

initial shock of landing to resiliently support the The casing |02 has a portion ||0 of increased load. diameter providing an annular shoulder H2 l0 Heretofore this has been accomplished by a adapted to function as a stop to limit the exten- 10 liquid damping means for absorbing the initial sion of the strut. This enlarged portion ||0 of shock of landing and by a spring either enclosed the casing is apertured asv indicated at Ill, and l within or sleeved on the strut for receiving and threaded thereon is a. collar H6, the purpose of resiliently supporting the load after the initial which will hereinafter appear. l5 shock of landing has been absorbed. There are A casing H8, closed at its upper end as by a cap 15 yalso a few commercial shock absorbing struts |20 'having a concentric opening 22, and opened for airplanes wherein compressed air is used as at its lower end, telescopes the casing |02 and is a resilient medium for supporting the load after adapted to slide smoothly on the collar H6. The the initial shock of landing. However, in shock cap |20 is threaded in the upper end of the 20A absorbing struts of this character the airis casing and is secured against displacement by a 2o compressed throughout the entire stroke of the Welding bead |24 which alSO Sel'VeS t0 eeCtil/Cly strut and is not effective only after the initial seal the upper end of the casing against leakage. shock of landing. Accordingly, struts of this The lower end of the casing ||8 has an enlarged type are not to be confounded with the instantA portion |26 providing a packing chamber |28 5 invention wherein the resilient medium for supand an internal shoulder |30, preferably inclined. 25

porting the load is not effective until after the A ring |32 tted in the packing chamber' |28 'landing shock has been largely absorbed. abuts the inclined shoulder |30. This ring is An object of the invention is to provide a shock adapted to slide smoothly on the casing |02 and absorbing strut operative to absorb the shock of to cooperate with the shoulder H2 on the casing siliently support the load after the shock of packing chamber |28 also has therein suitable landing has been absorbed. Y packing rings |34 and a collar |38 held against Another object of the invention is to provide a displacement'by a retaining ring |38 threaded on shock absorbing strut having one medium eiecthe free end of the, packing chamber. The collar 35 tive for absorbing the initial shock of landing and |36 is adapted to slide smoothly on the casing 35 a separate and distinct medium eliective forl02and is provided with a gland |40 filled with a supporting the .load only aftertheinitial shock suitable packing material |42 for removing ldirt of landing. from casing |02 of the strut. This casing ||8 also A further object of the invention is to provide has a iilling opening |44 for the introduction' of 4o a shock absorber for an` airplane including uid liquid, and the opening is normally closed as by 40 metering means for absorbing the initial shock a plug |45.

of landing and air or gas under pressure for i short cylindricaltting M8 on thev back of resiliently supporting the load after absorptionf Zthe 'cap |20.includes a concentric sleeve |50 exof theianding shock has been effected. tending through the opening |22 in the cap- `45 Other objects of the invention Vwill appear from Locknuts |52 threaded on the sleeve clamp the 45 the. following description taken in connection ttng to the cap, and a plug |54 normally closwith the drawing forming a part of this speciiicaing the sleeve includes a check valve, not shown. tion, and in which: A double diametrical casing |56 provides, at Figure 1 is a vertical sectional view of a shock the junction between Athat portion of the casing 5o absorbing strut illustrating the strut in extended having the smaller diameter and'that portion oi 50 position; and the casing having a relatively larger diameter, an Figure 2 is a vertical sectional view of the 'same annular shoulder |58, the purpose of which will strut illustrated in Figure 1 in the compressed hereinafter appear. The upper end of the casing, position. or that end having the smaller diameter, is xedat The invention is shown in the drawing in an 1y secured to the tting IIB. The casing |56de- 55 landing without undesirable rebound and to re- H0 in limiting the extension of the strut. The 80.

plurality of apertures |68 for relieving pressurev on the fluid back of the piston during the compression stroke.

A floating annular piston |10, reciprocable on that portion of the casing |56 having the smaller diameter between the casing |56 and the casing H8, divides the casing I8 so as to provide a compressed air chamber |12 in the upper end of the strut and this chamber is provided with a suitable filling opening normally closed by a plug in-I cludinga check valve, not shown.

The piston |10 has on its head concentric grooves in which are iitting leak-proof cups |14 and |16 for inhibiting the passage of air from the chamber |12 past the piston. A shell |18 suitably secured' to the piston retains the cups against displacement. This shell is adapted to contain a small quantity of lubricant and is provided with a plurality of spaced small apertures '|80 through which lubricant may be fed to the piston. The -lubricant also provides a liquid seal for the air chamber |12. Suitably attached to' the back of the piston is a exible ring |82,

preferably rubber, providing a cushioned seat for y the piston when the piston is at rest or in fully extended position on the annular shoulder |58, and also suitably attached to the back of the piston is a similar flexible ring |84 providing a cushioned seat for the piston when engaged by the upper end of the casing |02, as when the strut is in the compressed position. l

The mode of operation of this strut is substantiallyy the same as that given for the preferred embodiment of the invention. However, for the purpose of continuity, the operation may be given as follows:

The initial impact of the landingcauses the pressure on the uid in the casing |02 to close' the valve |66. and thereafter the uidis forced through the orifice I| 62 in the piston |60 past the metering pin |08 into the casing |56, thence through the apertures |68 into the casing |62 back of the piston, and through the apertures I4 in the casing |02 into the casing ||8. This results ineiectively damping the initial shock of landing and in reducing to a minimum the pressure on the fluid in the strut. Upon absorption of a predetermined portion ofthe shock of landing,

.the upper end of the casing |02 'engages the back of thepiston |10 and thereupon the load is partially transferred to the piston |10. Movement of this piston |10 is resisted by thepressure on the air or gas contained in the chamber |12 to the end that the load is resiliently supported.

When the airplane takes off or ascends, the strut returns to its fully extended position and in assuming his position the air or /gas under pressure returns the piston |10 to its seaton the annular shoulder -|58 and the weight of the landing gear attached to the lower end of the-strut moves the casing downwardly until the stop ||2 thereon engages the ring |32.

While the invention has been described in con'- nection with one specific embodiment, the principles invplved are susceptible of numerous other applications that will readily occur to persons skilled in the art. -The invention is, therefore/to be limited only as indicated by the scope of the appended claim. y

Having thus described the various features of the'invention," what I claim as new and desire to secure by Letters Patent isyA shock strut comprising connected inner and outer casings arranged to telescope withl a lower casing of intermediate diameter, and a floating annular piston within the outer casing and sleeved on the inner casing and backed by a fluid pressure ,heavy enough to carry a taxying load and which is engaged by the end of the lower casing after the shock of landing has been absorbed, said strut having means for forcing liquid upwardly from the lower casing through a restricted orifice to absorb the shock of landing, and said inner and lower casings having openings through which the liquid thereafter can pass into the outer casing.

CARL V. JOHNSON. 

